Thanks to everyone for the prompt responses, it's much appreciated and I didn't honestly expect to receive any advice!
I guess I ruled out a malfunctioning remote as a possibility and was hoping for good news on a simple fix for the receiver. Here are the steps I took to troubleshoot before posting to the forum:
As soon as my Rotel stopped responding I powered it down using the main switch on the back, unplugged the power cord and waited 10 minutes per our local Rotel dealer. No dice, still nothing.
I then launched the Logitech software on my Mac, deleted the Rotel A/V receiver from the Harmony One list of devices, plugged the remote in to my Mac w/USB, updated the remote and confirmed the device had been deleted from the remote.
Next, I added a new device to the remote (Rotel RSX-1058, obviously), plugged it back in and updated it using the Logitech software. Still no luck.
My Harmony One still works flawlessly with my Rotel RDV-1092, Comcast/Motorola cable box, Samsung Smart TV, XBOX One and my iMac.
Makes me think it's not the remote though I wish it were, it's a much easier fix and won't leave me without a receiver should i need to send it out for repairs.
"Receiver-less for 2 months while my Rotel is sent in for $500 in repairs"